The present invention relates generally to tree shakers for harvesting nuts, fruits, and other tree-borne crops, and more specifically to an improved tree shaker head having an improved pivot assembly for connecting the clamping arm to the frame, which includes an integral stationary arm.
Tree shakers are known in the art for harvesting nuts, fruits, and other tree-borne products. Shakers typically employ a boom extending forwardly from a tractor or other device, with a shaker head present at the end of the boom for grasping a tree and imparting a shaking force to the tree. The shaker head comprises a clamping arm and a frame having an integral stationary arm, with the clamping arm pivotally attached to the frame by a pivot pin assembly.
The shaker head is positioned around a tree and when the hydraulically actuated ram on the clamp cylinder is energized the clamping arm pivots toward the stationary arm thereby causing pads on the inside of the shaker head to compress and conform round the trunk. The hydraulic system then sequences from the clamping circuit to the shaking circuit, launching the shaker head into a vigorous shaking pattern during which the crop of fruit or nuts rains down in a cloud of dust and debris. When the shake control is released dynamic braking is applied and the shaker head brakes hard to a stop. The shaker head is then unclamped and the unit moves onto another tree. This process is repeated, often several times a minute depending upon the tree spacing and operator until all trees in the orchard have been shaken. The shaking action of the device dislodges fruits, nuts, and other products, which then fall from the branches of the tree to be harvested. The shaking action is aggressive, with severe loads imparted to various components of the device, particularly within the shaker head.
The commonly used tree shaker typically comprises a frame having a hollow welded steel case structure which contains the drive sheave, drive belt, two or more eccentric rotating masses, one or more hydraulic cylinders which open and close the arms of the tree shaker and hydraulic hose routings. A hydraulic motor for driving the eccentric rotating masses typically mounts within or on the top of the case structure and is connected to a drive pulley. The frame has a stationary arm which is either affixed to the frame or is integral to the frame. Opposing the stationary arm is a clamping arm which attaches to the rear of the frame by a pivot pin. The clamping arm and the stationary arm apply a compressive force during the shaking process when a hydraulic cylinder is actuated, causing the clamp arm to pivot about the pivot pin and move toward the stationary arm, causing the clamping arm and stationary arm to close about a tree trunk. Once the arms of the head are closed about the tree trunk, vibration is initiated within the shaker head. Typically the shakers use stacked counter rotating eccentric mass energy wheels to generate the vibration or pulse, which is created by the rotation of an eccentric mass about a fixed common shaft.
It is to be appreciated that the various components of the shaker head are subjected to significant loading during the above described process, which is repeated almost immediately and repeatedly. In each sequence all components of the shaker head are twisted into alignment. As a result of this repeated sequence, various shaker head components are continually stressed and subject to wear and failure. The inventor herein has found that the pivot pin components and supporting structures are particularly subject to fatigue, wear, and failure as a result of the repeated and significant loading during operation of the shaker head.
The pivot pin, as well as the surrounding structure of the stationary arm and the clamp arm, are subjected to repeated cycles of loading and unloading during the vibration cycle. Because of the inevitable misalignment of the clamping arm with the stationary arm as the head repeatedly engages trees, the structural components at the pivot assembly of the clamping arm frame/stationary arm are subjected to tensional, compressional, and torsional loads. Given the severity and frequency of the imposed loads, it is not uncommon for the pivot pin bushings to pull completely through the structural plate of the stationary arm in less than a season of use of the shaker.